a. Field of the Invention
The present invention relates to image analysis apparatus for measuring the front of screen performance of a display device.
b. Related Art
An example of conventional image analysis apparatus for measuring front of screen performance comprises an array of fixed cameras. Each camera is equipped with its own lens. Calibration data varies from one camera to another as a function of the tolerance of the constituent components and of the position of the cameras relative to the target. Calibration is generally performed by placing a calibration target carrying a test image in place of the normal target. A computer system under the control of computer software then analyses the detected test images to determine the spatial calibration data for each camera/lens combination.
Another example of conventional image analysis apparatus for measuring front of screen performance comprises a camera which is moveable relative to the target to select different areas of the target. Yet another example of such apparatus comprises a moveable lens system for selectively directing different portions of the target towards a fixed camera. In both cases, the spatial calibration is again performed by placing a calibration target carrying a test image in place of the normal target, and analysing the detected test image to determine the calibration data for the camera.
Conventional image analysis tools, such as those described above, are too large for use as hand-held instruments. The user cannot therefore select different areas of the target for analysis without the use of complex and relatively slow positioning jigs.
In accordance with the present invention, there is now provided image analysis apparatus comprising: a two dimensional array of photodetectors having a known spatial geometry for receiving light from pixels of a display screen having a known pixel geometry; a memory for storing intensity values generated by the photodetectors in response to incident light from the pixels; means for mapping the phhotodetectors' spatial geometry onto the display screen's pixel geomtry; and a processor adapted to determine a performance parameter of the display screen as a function of the intensity values stored in the memory and of the photodetectors' mapped spatial geometry.